The authors examined human immunity indicators such as CD4, CD8, Natural Killer (NK) cell, IgG, IgA, and IgM, and heavy metals such as Pb, Cr, Cd to evaluate the health hazard of welders. We selected total 126 male subjects, 60 welders who had more than 5 year working history as an exposure group, and 66 office workers and medical college students as a control group. This immunity evaluation approach is the first newly designed study that has never been tried in past studios on welder's heath evaluation. And the results were as follows. 1. Total lymphocyte count of peripheral blood was significantly higher in welder group, 2,615+/-650 ea/microliter compared with 2,368+/-681 ea/microliter in control group (p<0.05). 2. The proportion of CD4, CD8, NK cell in welder group was 37 5+/-9.4%, 24.0+/-8.8%, and 21.0+/-9.5%, respectively, and 35.5+/-6.5%, 25.0+/-6.9%, and 19.6+/-8.8% in control group. CD4 and NK cell were slightly higher, and CD8 was slightly lower in welder group. But there was no statistical significance between two groups (p> or =0.05). 3. IgG, IgA, and IgM in welder group were 15.9 mg/dl, 2.7 mg/dl, and 1.5 mg/dl, respectively, and 15.6 mg/dl, 2.9 mg/dl and 1.7 mg/dl in control group. There was no statistical significance between two groups(p> or =0.05). 4. Blood lead, cadmium and chromium concentrations were 4.2+/-1.8 microgram/dl, 0.4+/-0.38 microgram/dl, 1.2+/-0.6 microgram/dl in welder group and 3.2+/-1.7 microgram/dl, 0.44+/-0.29 microgram/dl, 1.1+/-0.6 microgram/dl in control group, respectively, and these value were within normal ranges.